Rotor for an electric machine, electric machine for a vehicle, and vehicle
A rotor for an electric machine, includes a rotor lamination stack divided into a plurality of sectors, in each of which there is arranged a permanent magnet assembly which comprises two permanent magnets positioned in a V-shape symmetrically with respect to a plane of symmetry dividing the sector into two half-sectors, wherein an outer radius of the rotor lamination stack in a particular sector has a pair of local minimum values, which are formed symmetrically to one another with respect to the plane of symmetry in a half-sector of the sector.
1. A rotor for an electric machine, comprising:
a rotor lamination stack divided into a plurality of sectors;
a permanent magnet assembly arranged in each of the plurality of sectors and including two permanent magnets positioned in a V-shape symmetrically with respect to a plane of symmetry dividing each of the plurality of sectors into two half-sectors,
wherein an outer radius (r) of the rotor lamination stack in each of the plurality of sectors has a first pair of local minimum values, symmetrically to one another with respect to the plane of symmetry, at first positions,
the outer radius (r) of the rotor lamination stack in each of the plurality of sectors increases from each of the first positions to a boundary between two of the plurality of sectors adjacent to one another and has a first local maximum value at the boundary between two of the plurality of sectors adjacent to one another,
a maximum value (R max ) of the outer radius (r) over each of the plurality of sectors is situated on the plane of symmetry,
the outer radius (r) of the rotor lamination stack in each of the plurality of sectors has a second pair of local minimum values, symmetrically to one another with respect to the plane of symmetry, at second positions positioned between the first positions in a circumferential direction,
the outer radius (r) of the rotor lamination stack in each of the plurality of sectors decreases from the plane of symmetry to each of the second positions to have each of the second pair of local minimum values, and
the outer radius (r) of the rotor lamination stack in each of the plurality of sectors decreases from the boundary between two of the plurality of sectors adjacent to one another to each of the first positions to have each of the first pair of local minimum values.
2. The rotor according to claim 1 , wherein
the first pair of local minimum values is situated within a partial sector of one of the half-sectors, and
the partial sector is delimited in the circumferential direction by a position of an outermost point of the permanent magnet assembly in a radial direction and by a position of an outermost point of the permanent magnet assembly in the circumferential direction.
3. The rotor according to claim 1 , further comprising
a second permanent magnet assembly arranged in each of the plurality of sectors,
wherein an innermost point of the second permanent magnet assembly in a radial direction is situated outside an innermost point of the first permanent magnet assembly in the radial direction, and
each of the second pair of local minimum values is situated closer to the plane of symmetry in the circumferential direction relative to each of the first pair of local minimum values.
4. The rotor according to claim 3 , wherein
a second local maximum value is situated in each of the half-sectors between each of the first pair of local minimum values and each of the second pair of local minimum values.
5. The rotor according to claim 3 , wherein
the second permanent magnet assembly comprises another two permanent magnets arranged in a V-shape symmetrically with respect to the plane of symmetry.
6. The rotor according to claim 3 , wherein
the second permanent magnet assembly comprises a permanent magnet arranged orthogonally to the plane of symmetry.
7. The rotor according to claim 1 , wherein a course of the outer radius
in a region close to the plane of symmetry with respect to a minimum value follows the function
r
=
R
max
+
δ
0
-
δ
(
x
)
with
δ
(
x
)
=
α
cos
(
π
τ
p
x
)
and/or
in a region far from the plane of symmetry with respect to a minimum value follows the function
r
=
R
max
+
δ
0
-
δ
(
x
)
with
δ
(
x
)
=
β
1
-
2
τ
p
x
cos
(
π
τ
p
x
)
wherein
r describes a value of the outer radius,
R max describes a maximum value of the outer radius,
δ 0 describes a constant,
α, β each describe a positive proportionality factor,
τ p describes a distance in the circumferential direction between the planes of symmetry of the plurality of sectors adjacent to one another, and
x describes a coordinate in the circumferential direction with x=0 at a position of the plane of symmetry and
x
=
τ
p
2
at a central position between the planes of symmetry of the plurality of sectors adjacent to one another.
8. The rotor according to claim 1 , wherein
at least one of the first pair of local minimum values and the second pair of local minimum values is situated at a position in the circumferential direction where a magnetic leakage flux has a local maximum.
9. An electric machine for a vehicle, comprising
a stator and the rotor according to claim 1 mounted rotatably within the stator.
10. A vehicle, comprising
the electric machine according to claim 9 , which is designed to drive the vehicle.
11. The rotor according to claim 1 , wherein
the outer radius (r) of the rotor lamination stack in each of the plurality of sectors has a second local maximum value at a third position between each of the first positions and each of the second positions, and
the outer radius (r) of the rotor lamination stack in each of the plurality of sectors increases from each of the first positions to the third position and increases from each of the second positions to the third position to have the second local maximum value.